Remove the intersection of two list of sets from both lists, and append it to a new list in python

Question

I want to take the intersection of the list of sets x1,y2, remove them from both lists, then append it to a new list 'res'.
This is my code: (which works I think)

x1=[{'A'},{'B'},{'c'},{'D'}]
y1=[{'A'},{'B'},{'C'},{'d'}]
res=[]
for i in x1:
    if i in y1:
        res.append(i)
        x1.remove(i)
        y1.remove(i)
for i in y1:
    if i in x1:
        res.append(i)
        x1.remove(i)
        y1.remove(i)
print(x1,y1)

>[{'c'}, {'D'}] [{'C'}, {'d'}]

print(res)    

>[{'A'}, {'B'}]

I also tried this from that post:

>>> a = [1,2,3,4,5]
>>> b = [1,3,5,6]
>>> list(set(a) & set(b))
[1, 3, 5]

But when it's a list of sets, this gives errors:

x1=[{'A'},{'B'},{'c'},{'D'}]
y1=[{'A'},{'B'},{'C'},{'d'}]
res=[]
res.append(list(set(x1) & set(x2)))
print(x1,y1)
print(res)

>TypeError: unhashable type: 'set'

Is there any better methods to write this ?
Any help or suggestion would be appreciated.

Update:

x1=[{'A'},{'B'},{'c'},{'D'}]
y1=[{'A'},{'B'},{'C'},{'d'}]
x2= {e for i in x1 for e in i}
y2= {e for i in y1 for e in i}
z1 = x2.intersection(y2)
res = [{e} for e in z1]
x1=[{e} for e in x2-z1]
y1=[{e} for e in y2-z1]
print(x1,y1)
>[{'c'}, {'D'}] [{'C'}, {'d'}]
print(res)
>[{'A'}, {'B'}]

But when the set have size more then one:

x1=[{'A','B'},{'B'},{'c'},{'D'}]
y1=[{'A'},{'B'},{'C'},{'d'}]
x2= {e for i in x1 for e in i}
y2= {e for i in y1 for e in i}
z1 = x2.intersection(y2)
res = [{e} for e in z1]
x1=[{e} for e in x2-z1]
y1=[{e} for e in y2-z1]
print(x1,y1)
>[{'D'}, {'c'}] [{'C'}, {'d'}]
print(res)
>[{'B'}, {'A'}]

Which suppose output:

x1=[{'A','B'},{'B'},{'c'},{'D'}]
y1=[{'A'},{'B'},{'C'},{'d'}]
res=[]
for i in x1:
    if i in y1:
        res.append(i)
        x1.remove(i)
        y1.remove(i)
for i in y1:
    if i in x1:
        res.append(i)
        x1.remove(i)
        y1.remove(i)
print(x1,y1)
>[{'B', 'A'}, {'c'}, {'D'}] [{'A'}, {'C'}, {'d'}]
print(res)
[{'B'}]

How do I fix this?

shaik moeed · Answer 1 · 2019-11-15T05:52:51.230

1

Try this, by using .intersection() method.

>>> x1=[{'A'},{'B'},{'c'},{'D'}]
>>> _x1= {e for i in x1 for e in i}     
>>> _x1     
{'c', 'B', 'D', 'A'}
>>> y1=[{'A'},{'B'},{'C'},{'d'}]        
>>> _y1= {e for i in y1 for e in i} 
>>> _y1 
{'d', 'B', 'A', 'C'}
>>> z1 = _x1.intersection(_y1) # intersection

Output:

>>> [{e} for e in z1]   
[{'B'}, {'A'}]

>>> print(x1,y1)
[{'c'}, {'D'}] [{'C'}, {'d'}]

Explanation:

Converted list of sets to set and store them into a temporary variable and used .intersection() provided by built-in function set().
Finally, converted to your required format(i.e., list of sets)

edited Nov 15 '19 at 05:52

answered Nov 15 '19 at 05:07

shaik moeed

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I finally figured it out, Thanks! – Ethan Nov 15 '19 at 05:52
I think using this method seems still have some bugs, please check the update – Ethan Nov 15 '19 at 17:19
@Manx I have stored in `_x1`, `_y1`, i guess u haven't observed the previous edit. – shaik moeed Nov 16 '19 at 09:58

score 1 · Accepted Answer · answered Nov 15 '19 at 05:15

Convert those lists of sets into sets of frozensets, take the intersection and then convert back:

x1=[{'A'},{'B'},{'c'},{'D'}]
y1=[{'A'},{'B'},{'C'},{'d'}]

def list_of_sets_to_set_of_frozensets(l):
    return set(map(frozenset, l))

def set_of_frozensets_to_list_of_sets(s):
    return list(map(set, s))

res = set_of_frozensets_to_list_of_sets(list_of_sets_to_set_of_frozensets(x1) & list_of_sets_to_set_of_frozensets(y1))

print(x1,y1)
print(res)

Remove the intersection of two list of sets from both lists, and append it to a new list in python

2 Answers2